In a 5 players game in which I
Your worst move ever? Or, the move that made you drink until the end of the game...
In a 5 players game in which I drafted the Tyrells, I lost Highgarden to the Greyjoys in the first turn! First time I saw that move... It took me 5 turns to take back HighGarden and, since turn 1, I have been drinking non-stop in a begging and depressing manner (Whyyyyyyyyyyyy, bburrrp).
This will not happen again lol.
Attacking the Martell fleet on turn 1 with one baratheon ship using the AGOT housecards.
And forgetting Arianne Martell's ability (kill a units if you lose).
This set us both back 1 ship on turn 1. Things went downhill for both of us from there.
A turn in which I as Grayjoy could have won on either of my first two march orders but was too focused on my "third march for the win" tactic to notice and then lost to Stark on the same turn as she took her seventh city before my final march. (the lady in question had a six game winning streak exented by that over the rest of our long time gamer group and hasn't let us live it down yet 
)
I trusted another player.... 
In my last 2 games of GoT, I played Tyrell again twice. And I managed to still lose my capital first turn in the first game... And to lose it 2nd turn in the 2nd game... Sniff, I tought I have learned...